[SystemSafety] 2012 Super Puma Ditchings

[Peter Bernard Ladkin]

On 2014-06-13 11:21 , Andrew Rae wrote:
> ....Did you notice that the accident report has a huge volume of
> analysis looking at why the original
> finite element modelling of the lubrication shaft underestimated the stresses, but seems to accept
> the incorrectly wired switch as
> just one of those things that happens? 

I probably would have if I'd actually looked at the report :-)

(I hope to get around to it next week, but I am a little tied up at the moment.)

> No recommendations are made about change management, or obsolescence management. 

As I understand it, commercial flight operators are nowadays supposed to have a "Safety Management
System" (SMS) in place.

> I'd be highly surprised if there weren't processes supposed to address all three of these, so
> there's a step back again to ask why they didn't happen or didn't work.

Spot on. I would take you to be talking about the SMS and asking why it didn't work.

> Is this one of those cases where some use of accident modelling would really help the investigators?
> A simple AcciMap or Why-Because Graph of the causes mentioned in the report
> would find two nodes connecting into the outcome (the lubrication failure and the backup system
> "failure"), one with a long web of causes, and the other barely investigated.

Well, I'd think so, but then I would, wouldn't I?

I think of Accimaps more as a visual presentation of causal conclusions than a modelling or
investigatory method. I note, though, that what you suggest Accimaps or a WBG could show is actually
some property of the causal graph, and in our experience enabling such observations is very
dependent on the layout used. The ATSB used Accimaps first in the Lockhart River report and their
Accimaps got to be visually quite confusing with more than 15 or 20 nodes. Whereas WBGs with 20
nodes seem trivial and they remain quite clear up to at least 70 or 80 nodes. That's in large part
due to the layout engine. I have thought for many years that the importance of presentation is
underestimated. But I still don't seem to be able to convince many colleagues of that.

PBL

Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany
Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de